High Energy Cosmic Ray Events Research Articles

Double Higgs mechanisms, supermassive stable particles and the vacuum energy

In the present work, a hidden scenario which cast a long-lived superheavy particle [Formula: see text] and simultaneously an extremely light particle [Formula: see text] with mass [Formula: see text] eV is presented. The potential energy [Formula: see text] of the particle [Formula: see text] models the vacuum energy density of the universe [Formula: see text]. On the other hand, the [Formula: see text] particle may act as superheavy dark matter at present times and the products of its decay may be observed in high energy cosmic ray events. The hidden sector proposed here include light fermions with masses near the neutrino mass [Formula: see text] eV and superheavy ones with masses of the order of the GUT scale, interacting through a hidden SU(2)L interaction which also affects the ordinary sector. The construction of such combined scenario is nontrivial since the presence of light particles may spoil the stability of the heavy particle [Formula: see text]. However, double Higgs mechanisms may be helpful for overcoming this problem. In this context, the stability of the superheavy particle [Formula: see text] is ensured due to chiral symmetry arguments elaborated in the text.

The meaning of the UHECR Hot Spots

In this paper we review all the up-to-date Ultra High Energy Cosmic Ray (UHECR) events reported by AUGER, the Telescope Array (TA) and AGASA in common coordinate maps. We also confirm our earliest (2008–2013) model, where UHECRs mostly comprise light nuclei (namely He, Be, B), which explains the Virgo absence and confirms M82 as the main source for the Northern TA Hot Spot. Many more sources, such as NGC253 and several galactic sources, are possible candidates for most of the 376 UHECR events. Several correlated maps, already considered in recent years, are reported to show all the events, with their statistical correlation values.

The cosmic ray veto system of the Mario Schenberg gravitational wave detector

The Mario Schenberg gravitational wave antenna is a spherical cryogenic resonant mass detector located at IFUSP, São Paulo. It is well known that cosmic rays interact with cryogenic resonant mass detectors generating acoustic signals. Depending on the shower energy, they could provide a substantial background noise which should be vetoed to reduce the false alarm rate. For this purpose, in December 2011, we have installed a cosmic ray veto system which is, since then, acquiring data. The cosmic ray veto system is composed of three particle detectors containing each one a scintillator, a photomultiplier and a tension divider.As the shower number of particles is used to define a threshold for the veto, it is important that the cosmic ray veto provides a linear response to high-energy cosmic ray events. The veto setup response was optimized and allows measurements up to 23,000 equivalent muon charge particles per square meter.We present here the experimental setup, its calibration and performance. Finally, to confirm the linearity of the data acquisition we show the measured particle multiplicity.

Ultra High Energy Cosmic Rays: Anisotropies and spectrum

The recent results of the Pierre Auger Observatory on the possible correlation of Ultra High Energy Cosmic Rays events and several nearby discrete sources could be the starting point of a new era with charged particles astronomy. In this paper we introduce a simple model to determine the effects of any local distribution of sources on the expected flux. We consider two populations of sources: faraway sources uniformly distributed and local point sources. We study the effects on the expected flux of the local distribution of sources, referring also to the set of astrophysical objects whose correlation with the Auger events is experimentally claimed.

ACTIVE GALACTIC NUCLEI: SOURCES FOR ULTRA HIGH ENERGY COSMIC RAYS

Ultra high energy cosmic ray events presently show a spectrum, which we interpret here as galactic cosmic rays due to a starburst, in the radio galaxy Cen A which is pushed up in energy by the shock of a relativistic jet. The knee feature and the particles with energy immediately higher in galactic cosmic rays then turn into the bulk of ultra high energy cosmic rays. This entails that all ultra high energy cosmic rays are heavy nuclei. This picture is viable if the majority of the observed ultra high energy events come from the radio galaxy Cen A, and are scattered by intergalactic magnetic fields across much of the sky.

Neutrino, photon interaction in unparticle physics

We investigate the impact of unparticle physics on the annihilation of relic neutrinos with the neutrinos identified as primary source of ultra high energy (UHE) cosmic ray events, producing a cascade of photons and charged particles. We compute the contribution of the unparticle exchange to the cross-sections νν¯→γγ and νν¯→ff¯ scattering. We estimate the neutrino–photon decoupling temperature from the reaction rate of νν¯→γγ. We find that the inclusion of unparticles can in fact account for the flux of UHE cosmic rays and can also result in the lowering of neutrino–photon decoupling temperature below the QCD phase transition for unparticle physics parameters in a certain range. We calculate the mean free path of these high energy neutrinos annihilating themselves with the relic neutrinos to produce vector, axial-vector and tensor unparticles.

On a possible photon origin of the most-energetic AGASA events

In this work the ultra high energy cosmic ray events recorded by the AGASA experiment are analyzed. With detailed simulations of the extensive air showers initiated by photons, the probabilities are determined of the photonic origin of the 6 AGASA events for which the muon densities were measured and the reconstructed energies exceeded 1020 eV. On this basis a new, preliminary upper limit on the photon fraction in cosmic rays above 1020 eV is derived and compared to the predictions of exemplary top-down cosmic-ray origin models.

EAS experiment on board the Airbus A380

We consider taking the opportunity of about 10,000 hours of test flights of the Airbus A380, and to install in the passenger area detectors for high energy cosmic ray events. The altitude of 10 km (250 g/cm 2 ) presents the opportunity to measure EAS originating from heavy primaries to energies exceeding 10 7 GeV, and also the proton component beyond the energy of the knee arriving without interaction. At the flight altitude iron originated EAS are well developed and by registering their lateral distribution in the 70 meters long cabin it will be possible to distinguish them from proton originated EAS. The hadron component of EAS (registered as number of secondary hadrons produced in the detector) would help in discrimination and energy estimation. On the other hand, the detection of high energy protons (without EAS) would enable us to measure the high energy proton spectrum. The proton energy would be estimated via hadron multiplicity in single interactions inside the detector. We propose to use about 60 modules of 0.5 m 2 of active detectors with scintillators to detect E-M component and a carbon target with lead layer to detect the hadronic component via neutron registrations.

Search for correlated high energy cosmic ray events with CHICOS

We present the results of a search for time correlations in high energy cosmic ray data (primary E > 1014 eV) collected by the California HIgh school Cosmic ray ObServatory (CHICOS) array. Data from 60 detector sites spread over an area of 400 km2 were studied for evidence of isolated events separated by more than 1 km with coincidence times ranging from 1 µs up to 1 s. The results are consistent with the absence of excess coincidences except for a 2.9σ excess observed for coincidence times less than 10 µs. We report upper limits for the coincidence probability as a function of coincidence time.

Prospects for radio detection of ultra-high energy cosmic rays and neutrinos

The origin and nature of the highest energy cosmic ray events is currently the subject of intense investigation by giant air shower arrays and fluorescent detectors. These particles reach energies well beyond what can be achieved in ground-based particle accelerators and hence they are fundamental probes for particle physics as well as astrophysics. One of the main topics today focuses on the high energy end of the spectrum and the potential for the production of high-energy neutrinos. Above about 10 20 eV cosmic rays from extragalactic sources are expected to be severely attenuated by pion photoproduction interactions with photons of the cosmic microwave background. Investigating the shape of the cosmic ray spectrum near this predicted cut-off will be very important. In addition, a significant high-energy neutrino background is naturally expected as part of the pion decay chain which also contains much information. Because of the scarcity of these high-energy particles, larger and larger ground-based detectors have been built. The new generation of digital radio telescopes may play an important role in this, if properly designed. Radio detection of cosmic ray showers has a long history but was abandoned in the 1970s. Recent experimental developments together with sophisticated air shower simulations incorporating radio emission give a clearer understanding of the relationship between the air shower parameters and the radio signal, and have led to resurgence in its use. Observations of air showers by the SKA could, because of its large collecting area, contribute significantly to measuring the cosmic ray spectrum at the highest energies. Because of the large surface area of the moon, and the expected excellent angular resolution of the SKA, using the SKA to detect radio Cherenkov emission from neutrino-induced cascades in lunar regolith will be potentially the most important technique for investigating cosmic ray origin at energies above the photoproduction cut-off.

Observability of neutron events above the Greisen–Zatsepin–Kuzmin cut-off due to violation of Lorentz invariance

The clustering of ultra high energy cosmic ray events suggests that they have originated from compact sources. One of the possible physical mechanisms by which ultra high energy nuclei reach the Earth from far away astrophysical sources (quasars or BL Lac objects) evading the Greisen–Zatsepin–Kuzmin (GZK) cut-off is by violation of Lorentz invariance. Assuming that there is violation of Lorentz invariance, we calculate the expected number of neutron events from some of the EGRET sources (including γ-ray loud BL Lac objects) which can be correlated in direction with ultra high energy cosmic ray events observed by AGASA above energy 4×1019 eV. We present in this Letter what AGASA should see in future if violation of Lorentz invariance is responsible for the propagation of ultra high energy cosmic rays having energies above the GZK cut-off when there is a correlation of EGRET sources with the ultra high energy cosmic ray events.

Anisotropy at the end of the cosmic ray spectrum?

The starburst galaxies M82 and NGC253 have been proposed as the primary sources of cosmic rays with energies above ${10}^{18.7}\mathrm{eV}.$ For energies $\ensuremath{\gtrsim}{10}^{20.3}\mathrm{eV}$ the model predicts strong anisotropies. We calculate the probabilities that the latter can be due to chance occurrence. For the highest energy cosmic ray events in this energy region, we find that the observed directionality has less than 1% probability of occurring due to random fluctuations. Moreover, during the first 5 years of operation at Auger, the observation of even half the predicted anisotropy has a probability of less than ${10}^{\ensuremath{-}5}$ to occur by chance fluctuation. Thus, this model can be subject to test at very small cost to the Auger priors budget and, whatever the outcome of that test, valuable information on the galactic magnetic field will be obtained.

SELECTED TOPICS IN PLANCK-SCALE PHYSICS

We review a few topics in Planck-scale physics, with emphasis on possible manifestations in relatively low energy. The selected topics include quantum fluctuations of spacetime, their cumulative effects, uncertainties in energy–momentum measurements, and low energy quantum-gravity phenomenology. The focus is on quantum-gravity-induced uncertainties in some observable quantities. We consider four possible ways to probe Planck-scale physics experimentally: (i) looking for energy-dependent spreads in the arrival time of photons of the same energy from GRBs; (ii) examining spacetime fluctuation-induced phase incoherence of light from extragalactic sources; (iii) detecting spacetime foam with laser-based interferometry techniques; (iv) understanding the threshold anomalies in high energy cosmic ray and gamma ray events. Some other experiments are briefly discussed. We show how some physics behind black holes, simple clocks, simple computers, and the holographic principle is related to Planck-scale physics. We also discuss a formulation of the Dirac equation as a difference equation on a discrete Planck-scale spacetime lattice, and a possible interplay between Planck-scale and Hubble-scale physics encoded in the cosmological constant (dark energy).

Design, fabrication, and test of a fast scintillation detector preamplifier

A fast scintillation detector preamplifier is designed, which uses an operational video amplifier (type: LM733). Despite its simplicity, the preamplifier exhibits good noise and speed parameters. The amplifier is specially designed for an extensive air shower experiment [T. Bezboruh, K. Boruah, and P. K. Boruah, Nucl. Instrum. Methods Phys. Res. A 410, 206 (1998); Astropart. Phys. 11, 395 (1999)], Gauhati University, Assam, India. Plastic scintillators and fast photomultiplier tubes are used in the experiment to detect ultra high energy cosmic ray events. Here we report the characteristics of the amplifier including the hardware and its performances in the experiment.

Directional clustering in highest energy cosmic rays

An unexpected degree of small-scale clustering is observed in highest-energy cosmic ray events. Some directional clustering can be expected due to purely statistical fluctuations for sources distributed randomly in the sky. This creates a background for events originating in clustered sources. We derive analytic formulas to estimate the probability of random cluster configurations, and use these formulas to study the strong potential of the HiRes, Auger, Telescope Array and EUSO-OWL-AirWatch facilities for deciding whether any observed clustering is most likely due to nonrandom sources. For a detailed comparison to data, our analytical approach cannot compete with Monte Carlo simulations, including experimental systematics. However, our derived formulas do offer two advantages: (i) easy assessment of the significance of any observed clustering, and most importantly, (ii) an explicit dependence of cluster probabilities on the chosen angular bin size.

Farrar and Biermann Reply:

We discuss the rationale for the energy cuts used in the previous study of directional correlation of the five highest energy cosmic ray events with compact, radio quasars. We check the consistency of the next three most energetic events which just missed those cuts, with the correlation hypothesis. Agreement between expected and observed properties of these events is good.

Are high energy cosmic rays magnetic monopoles?

We argue that the hypothesis of magnetic monopoles as being the highest energy cosmic ray events is unlikely. For reasonable values of the monopole mass both the observed spectrum and the arrival direction disagree with observation. Our conclusions could be evaded if (i) monopoles are accelerated in the extragalactic magnetic fields to energies much above the observed energies and (ii) the amount of energy that the monopole yields to the shower is small.

High energy neutralinos from topological defects

Abstract We present a new solution for the problem of ultra high energy cosmic ray events with energy up to 3.1020 eV. Various authors have considered that these events are caused by the decay of supermassive particles emitted by topological defects formed during the symmetry breaking of a GUT. However, in the framework of supersymmetric theories, the decay of topological defects should produce not only “normal” matter like protons, photons and neutrinos but also supersymmetric matter. The supersymmetric particles decay producing neutralino as the lightest supersymmetric particle. We present cross sections of ultra high energy neutralinos with matter and estimate the energy density of neutralinos produced by superconducting strings.

FELIX, a full acceptance detector for the CERN LHC

Plans for FELIX, a full acceptance detector for the future CERN Large Hadron Collider (LHC), are described. The physics goals include detailed studies of the strong interactions (QCD), the forward energy flow and diffractive processes (Pomeron interactions), electroweak rapidity gaps, and elastic scattering. The precise measurement of particle production at a centre-of-mass energy of 14 TeV, well above the cosmic ray “knee”, will be fundamental for the interpretation of the highest energy cosmic ray events and may clarify some of the anomalies indicated by some cosmic ray experiments. The magnetic architecture and some of the design issues are briefly reviewed.

Possible Extragalactic Sources of the Highest Energy Cosmic Raysa

We give an outline of possible extragalactic explanations of the highest energy cosmic ray events. We give a classification of the possible particles which could have caused the events and try to find suitable sources for each class. In contrast to some previous investigations of other authors, we find a possible candidate of a local FR-II radio galaxy close to the Fly's Eye event, and less powerful active galaxies close to the AGASA event. We also note the interesting coincidence that we have strong, distant quasars inside the arrival direction error regimes of both the Fly's Eye and AGASA event. We briefly discuss the consequences for the cosmic ray spectrum and composition at highest energies, which could be investigated by future experiments.